1. Department of Obstetrics and Gynecology, Wuxi Maternal and Child Health Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214002, PR China
2. Department of Obstetrics, The Third Xiangya Hospital of Central South University, Changsha, Hunan 410013, PR China
3. Central Lab, Wuxi Maternal and Child Health Hospital Affiliated to Nanjing Medical University, Wuxi, Jiangsu 214002, PR China